Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive non metal and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.

Key point: The chalcogens  are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po).

Oxygen was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774, but Priestley is often given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion.

Oxygen is a highly reactive element and is capable of combining with most other elements. It is required by most living organisms and for most forms of combustion. Impurities in molten pig iron are burned away with streams of high pressure oxygen to produce steel.

Oxygen can also be combined with acetylene (C2H2) to produce an extremely hot flame used for welding. Liquid oxygen, when combined with liquid hydrogen, makes an excellent rocket fuel. Ozone (O3) forms a thin, protective layer around the earth that shields the surface from the sun’s ultraviolet radiation. Oxygen is also a component of hundreds of thousands of organic compounds.


Liquid Oxygen is one of the physical forms of elemental oxygen. It is abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries. 

The first measurable quantity of liquid oxygen was produced by Polish professors Zygmunt Wróblewski and Karol Olszewski (Jagiellonian University in Kraków) on April 5, 1883.


Some of the physical Properties of Liquid Oxygen are;

1. Liquid oxygen has a pale blue color.                                                                   2. It is strongly paramagnetic; it can be suspended between the poles of a powerful horseshoe magnet.                                                                          3.  Liquid oxygen has a density of 1.141 g/cm3 (1.141 kg/L or 1141 kg/m3) 4.  4. It is cryogenic with a freezing point of 54.36 K (−218.79 °C; −361.82 °F) and a boiling point of 90.19 K (−182.96 °C; −297.33 °F) at 101.325 kPa (760 mmHg).                                                                                                                    5.Liquid oxygen has an expansion ratio of 1:861 under 1 standard atmosphere (100 kPa) and 20 °C (68 °F) and because of this, it is used in some commercial and military aircraft as transportable source of breathing oxygen.

Key Point:    cryogenics is the study of the production and behaviour of materials at very low temperatures.       

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